(1) Field of the Invention
The present invention relates to a data recording and reproducing apparatus which encodes video and audio signals to record and reproduce the signals to and from a recording medium.
(2) Description of the Related Art
When a digital broadcast signal is recorded to a hard disk and an optical disc recording medium, the digital broadcast signal is usually recorded in a format that is in conformity with the broadcast standards. For example, for the recording of video and audio signals, which uses a BD (Blu-ray Disc) medium known as a large-capacity optical disc, standards which are called the BDAV (BD Audio/Visual) format have been established. When this format is used, a received digital broadcast is recorded to a BD medium based on a certain compression format (encoding format) without changing the compression format (encoding format). To be more specific, a video signal is received by the MPEG2 format, and the video signal is then recorded to a BD medium without changing the format.
On the other hand, for BD media, standards used for read-only media, which are called the BDMV (BD MoVie) format, have been established. Because this format adopts the H.264 method whose compression ratio is higher than that of the MPEG2 format, a video signal is recorded with higher efficiency. Therefore, if a received video signal based on the MPEG2 format is transcoded to a signal based on the H.264 format whose compression ratio is high before the transcoded signal is recorded to a medium, it is possible to save the capacity of the medium, and thereby to improve the efficiency in the use.
However, if a digital broadcast signal is transcoded to that based on a high compression format in real time with the digital broadcast signal being received, a high-performance encoder (transcoder) is required. In particular, because a high-definition (HD) broadcast signal contains the huge amount of information, it is not easy to satisfactorily transcode this signal. For this reason, if the digital broadcast signal is transcoded not in real-time but in delayed time using an unused time of a data recording and reproducing apparatus, a load on the encoder (transcoder) is reduced, and consequently the feasibility is increased.
For example, Japanese Patent Application Laid-Open No. 2001-110125 proposes a technique for changing a compression format without increasing product costs, and with data (video/audio data) being transferred at a normal speed. Here, compressed data which is inputted at a transfer rate exceeding the normal speed is recorded to a medium without changing the compression format. After that, using an unused time for an access to the medium, the compressed data is reproduced from the medium to transcode the data, at the normal speed, to data based on a different compression format, and then the transcoded data is recorded to the medium again.